Panel filter



FIG. 1 is a perspective view of a panel filter embodying our new design;

FIG. 2 is a front side elevational view thereof, the rear side elevational view being a mirror image thereof;

FIG. 3 is a right end elevational view thereof;

FIG. 4 is a left end elevational view thereof;

FIG. 5 is a top plan view thereof; and,

FIG. 6 is a bottom plan view thereof. 

The ornamental design for a panel filter, as shown and described. 